Ethernet is a representative standard of wired bus topology packet networks. Ethernet based on up to 10 Mbps uses a bus topology network. However, when a data rate exceeds 100 Mbps, channel distortion becomes severe, and it is not possible to perform high-speed communication without using an equalizer.
In a bus topology network, a plurality of receivers should be able to receive a packet transmitted by a transmitter. However, since it is not possible to know in advance to which receiver the transmitter transmits a packet, equalizer training is difficult. Therefore, a network of 100 Mbps or more uses a star topology network (star network). Since all Ethernet nodes in a star network communicate with other network nodes through a switch, when a node transmits data, the corresponding receivers are unified as a receiver in the switch, and only an equalizer for a single transceiver link is required. Therefore, it is possible to previously perform equalizer training for a channel between the node and the switch, and high-speed data transmission can be performed on the basis of the equalizer training.